Four-coordinate and pseudo five-coordinate Hg(II) complexes of a new bidentate phosphorus ylide: X-ray crystal structure and spectral characterization

Article abstract of DOI:10.1016/j.jorganchem.2010.02.029

The reaction of Ph₂PCH₂PPh₂ (dppm) with BrCH₂C(O)C₆H₄NO₂ in chloroform produces the new phosphonium salt [Ph₂PCH₂PPh₂CH₂C(O)C₆H₄NO₂]Br (1). Further, by reacting the phosphonium salt with appropriate base the bidentate phosphorus ylide, Ph₂PCH₂PPh₂{double bond, long}C(H)C(O)C₆H₄NO₂ (2) was obtained. The reaction of ligand 2 with mercury(II) halides in dry methanol led to the formation of the P, C-coordinated mononuclear complexes [HgX₂(Ph₂PCH₂PPh₂C(H)C(O)C₆H₄NO₂)] [X = Cl (3), Br (4), I (5)]. Characterization of the obtained compounds was performed by elemental analysis, IR, ¹H, ³¹P, and ¹³C NMR. The X-ray crystal structure of 5 as well as the complex derived from crystallization of 4 in DMSO, [HgBr₂(Ph₂PCH₂PPh₂C(H)C(O)C₆H₄NO₂)(DMSO)] (6), is reported. In both complexes 5 and 6 the title ylide is coordinated through the ylidic carbon and the phosphine atom. However, in compound 6 the Hg-C bond length is considerably weakened due to coordination of DMSO molecule to the metal ion and locating of ylidic carbon atom in the axial position of the resulting trigonal bipyramidal complex. Theoretical studies on ligand and all complexes at DFT (B3LYP) level of theory are also reported. The results show that the addition of DMSO molecule to the compound 4 and formation of compound 6 is energetically favored.

Full text of DOI:10.1016/j.jorganchem.2010.02.029

Journal of Organometallic Chemistry 695 (2010) 1441–1450
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Four-coordinate and pseudo five-coordinate Hg(II) complexes of a new bidentate
phosphorus ylide: X-ray crystal structure and spectral characterization
a
a
b
Seyyed Javad Sabounchei a, , Sepideh Samiee , Sadegh Salehzadeh , Zabihollah Bolboli Nojini ,
*
Elisabeth Irran c
a Faculty of Chemistry, Bu-Ali Sina University, Hamedan 65174, Iran
b Department of Chemistry, Faculty of Science, Shahid Chamran University, Ahvaz, Iran
c Institut für Chemie-Anorganische Festkörperchemie, Technische Universität Berlin, Strabe des 17. Juni 135, D-10623 Berlin, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
The reaction of Ph2PCH2PPh2 (dppm) with BrCH2C(O)C6H4NO2 in chloroform produces the new phospho-
nium salt [Ph2PCH2PPh2CH2C(O)C6H4NO2]Br (1). Further, by reacting the phosphonium salt with appro-
priate base the bidentate phosphorus ylide, Ph2PCH2PPh2@C(H)C(O)C6H4NO2 (2) was obtained. The
reaction of ligand 2 with mercury(II) halides in dry methanol led to the formation of the P, C-coordinated
mononuclear complexes [HgX2(Ph2PCH2PPh2C(H)C(O)C6H4NO2)] [X = Cl (3), Br (4), I (5)]. Characterization
of the obtained compounds was performed by elemental analysis, IR, 1H, 31P, and 13C NMR. The
X-ray crystal structure of 5 as well as the complex derived from crystallization of 4 in DMSO,
[HgBr2(Ph2PCH2PPh2C(H)C(O)C6H4NO2)(DMSO)] (6), is reported. In both complexes 5 and 6 the title ylide
is coordinated through the ylidic carbon and the phosphine atom. However, in compound 6 the Hg–C
bond length is considerably weakened due to coordination of DMSO molecule to the metal ion and locat-
ing of ylidic carbon atom in the axial position of the resulting trigonal bipyramidal complex. Theoretical
studies on ligand and all complexes at DFT (B3LYP) level of theory are also reported. The results show that
the addition of DMSO molecule to the compound 4 and formation of compound 6 is energetically favored.
Ó 2010 Elsevier B.V. All rights reserved.
Received 17 November 2009
Received in revised form 22 February 2010
Accepted 25 February 2010
Available online 1 March 2010
Keywords:
Bidentate phosphorus ylide
Mercury(II) halides
X-ray crystal structure
1. Introduction
lar-electronic structure of the ylide due to the presence of addi-
tional keto stabilization. Coordination of ligands towards Hg(II)
Phosphorus ylides are important reagents in organic chemistry,
especially in the synthesis of naturally occurring products with
biological and pharmacological activities [1]. These compounds
have been used as reducing agents in coordination chemistry.
The utility of metalated phosphorus ylides in synthetic chemistry
has assumed importance since, in nature’s mercury detoxification
process, the initial Hg–C bond cleavage involves the increase in
the coordination number around Hg [22]. Furthermore, evidence
for new classes of metal-binding motifs in enzymes, transcription
factors, and regulatory proteins emphasize the need for structural
insights about local Hg(II) coordination environments [23].
The investigation of the reactivity and coordination chemistry
of carbonyl stabilized ylides is research field of our group [18–
19,24]. We have now focused our attention to new bidentate phos-
phorus ylides. We aim to expand the scope of complexes with this
type of bidentate phosphorus ylides, and to study the bonding
properties of this type of ligands. In this context, we report the
reactivity of 2 towards mercury(II) halides.
has been well documented [2–5]. The a-keto stabilized ylides de-
rived from bisphosphines, viz., Ph2PCH2PPh2@C(H)C(O)R, Ph2P-
(CH2)2PPh2@C(H)C(O)R (R = Me, Ph or OMe) [6] and PhC(O)C(H)@
PPh2CH2CH2PPh2@C(H)C(O)Ph [7] form an important class of hy-
brid ligands containing both phosphine and ylide functionalities,
and can exist in ylidic and enolate forms. These ligands can there-
fore engage in different kinds of bonding with metal ions [6–17].
Hg(II) forms C-coordinated complexes with X-C6H4C(O)C(H)@
PAr3 (X = Cl and NO2; Ar = phenyl and p-tolyl) [18,19] and
Ph3P@C(H)CO(OEt) [20]. On the other hand, regiospecific O-coordi-
nation of the acetyl oxygen has been observed for the reaction of
Hg(II) halides with Ph3P@C(COPh)(COMe) [21]. The remarkable
change in reactivity arises from a subtle variation in the molecu-
2. Experimental
2.1. Physical measurements and materials
All reactions were carried out under an atmosphere of dry nitro-
gen. Methanol was distilled over magnesium powder and diethyl
ether (Et2O) over a mixture of sodium and benzophenone just
* Corresponding author. Tel.: +98 8118272072; fax: +98 8118273231.
E-mail address: jsabounchei@yahoo.co.uk (S.J. Sabounchei).
0022-328X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.02.029

1442
S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
before use. All other solvents were reagent grade and used without
further purifications. Melting points were measured on a SMP3
apparatus. IR spectra were recorded on a Shimadzu 435-U-04 FT
spectrophotometer from KBr pellets. 1H, 13C and 31P NMR spectra
were recorded on 300 MHz Bruker and 90 MHz Jeol spectrometer
in DMSO-d6 or CDCl3 as solvent at 25 °C. Chemical shifts (ppm)
are reported according to internal TMS and external 85% phospho-
ric acid. Coupling constants are given in Hz. Elemental analysis for
C, H and N atoms were performed using a Perkin–Elmer 2400 ser-
ies analyzer.
2.4.3.1. [(2)HgCl2] (3). Yield: 0.152 g, 62%. M.p. 185–187 °C. Anal.
Calc. for C33H27Cl2HgNO3P2: C, 48.39; H, 3.32; N, 1.71. Found: C,
47.98; H, 3.11; N, 1.92%.
2.4.3.2. [(2)HgBr2] (4). Yield: 0.184 g, 68%. M.p. 197–199 °C. Anal.
Calc. for C33H27Br2HgNO3P2: C, 43.66; H, 3.00; N, 1.54. Found: C,
43.21; H, 3.04; N, 1.40%.
2.4.3.3. [(2)HgI2] (5). Yield: 0.240 g, 80%. M.p. >132 °C (decom-
poses). Anal. Calc. for C33H27I2HgNO3P2: C, 39.56; H, 2.72; N,
1.40. Found: C, 39.28; H, 2.85; N, 1.65%.
2.2. X-ray crystallography
2.4.3.4. [(2)HgBr2DMSO] (6). This compound was easily obtained
from the crystallization of compound 4 (0.091 g, 0.1 mmol) in
DMSO solution. The yellow crystals formed by the slow evapora-
tion of the solvent over several days. Yield: 0.093 g, 95%. M.p.
180 °C (decomposes). Anal. Calc. for C35H33Br2HgNO4P2S: C,
42.63; H, 3.34; N, 1.42. Found: C, 42.44; H, 3.41; N, 1.53%.
The single crystal X-ray diffraction analyses for complexes 5
and 6 were performed on an Oxford Diffraction Xcalibur S Sapphire
system at 150(2) K, using graphite monochromated Mo K
a X-ray
radiation (k = 0.7107 Å). The crystal structures were solved by di-
rect methods and refined by using SHELXS-97 and SHELXL-97 crystallo-
graphic software packages [25,26]. All non-hydrogen atoms were
refined anisotropically using reflections I > 2r(I). Hydrogen atoms
were located in ideal positions.
3. Results and discussion
3.1. Synthesis
2.3. Computational details
The reaction of dppm with 4-nitrophenacyl bromide (prepared
by reacting 4-nitroacetophenone with bromide in glacial acetic
acid) for 2 h (1:1 molar ratio) in CHCl3 gave the phosphonium salt
(1) in good yield as a orange solid. Further treatment with triethyl
amine led to elimination of [Et3NH]Br, giving the free ligand (2)
(Scheme 1). The reactions of Hg(II) halides with bidentate phos-
phorus ylide, Ph2PCH2PPh2@C(H)C(O)C6H4NO2 in 1:1 molar ratio
yielded P, C-chelated complexes. The reaction of complex 4 by
DMSO obtained complex 6 containing coordinated DMSO molecule
(Scheme 2).
The calculations were carried out at the density functional the-
ory (DFT) level, using the B3LYP [27,28] exchange-correlation func-
tional, with a LanL2DZ basis set [29] for compounds 5 and 6 and
CEP-121G [30] for all compounds. The latter basis sets includes
effective core potentials (ECP) for both the mercury and phospho-
rus atoms as well as halide (Brꢀ and Iꢀ) ions. The program GAUSSIAN
03 was employed for all calculations [31]. The molecular structures
of 2–8 in the ground state were fully optimized. Atomic coordi-
nates for DFT calculations were obtained from the data of the X-
ray crystal structure analyses of compounds 5 and 6.
3.2. Spectroscopy
2.4. Synthesis of compounds
The IR data confirm the complete formation of the carbonylic
ylide with the disappearance of the phosphonium CO band at
1684 cmꢀ1 and the presence of a new strong CO band relative to
a carbonyl stabilized ylide at 1524 cmꢀ1 [14]. As noted previously
[32], the coordination of the ylide through carbon or oxygen causes
2.4.1. Synthesis of [Ph2PCH2PPh2CH2C(O)C6H4NO2]Br (1)
A solution of bis(diphenylphosphino)methane (dppm) (0.192 g,
0.5 mmol) and 4-nitrophenacyl bromide (0.152 g, 0.5 mmol) in
chloroform (17 ml) was stirred at room temperature for 2 h. The
yellow solution was concentrated under reduced pressure to
5 ml, and diethyl ether (20 ml) was added. The orange solid formed
was filtered, washed with diethyl ether (20 ml) and dried under re-
duced pressure. Yield: 0.276 g, 88%. M.p. 210–212 °C. Anal. Calc. for
C33H28BrNO3P2: C, 63.07; H, 4.49; N, 2.23. Found: C, 62.98; H, 4.40;
N, 2.39%.
a significant increase or decrease, respectively, in the m(C@O) fre-
quency. The infrared absorption bands observed for the three com-
plexes around 1585 cmꢀ1 indicate coordination of the ylide
through ylidic carbon atom (Table 1). It should be noted that the
appearance of a weak bond probably associated to
m(S@O) at
1016 cmꢀ1 in the IR spectrum of compound 6 is unique difference
between the IR spectra of compounds 4 and 6 [33].
The 31P NMR spectrum of 1 exhibits two doublets at 20.70 and
ꢀ29.52 ppm, with a coupling constant 2JP–P of 64.5 Hz, attributable
to PCH2 and PPh2 groups, respectively. The 1H NMR spectrum
2.4.2. Synthesis of [Ph2PCH2PPh2@C(H)C(O)C6H4NO2] (2)
The resulting phosphonium salts (1) (0.314 g, 0.5 mmol) were
treated with triethyl amine (0.5 ml) in toluene (15 ml). The triethyl
amine hydrobromide was filtered off. Concentration of the toluene
layer to 5 ml and subsequent addition of petroleum ether (25 ml)
results in the precipitation of ligands as yellow solids. Yield:
0.222 g, 81%. M.p. 144–147 °C. Anal. Calc. for C33H27NO3P2: C,
72.39; H, 4.97; N, 2.56. Found: C, 72.57; H, 5.11; N, 2.78%.
2
exhibits a doublet at 6.10 ppm, with a JP–H of 12.81 Hz, related
to a CH2 group of a 4-nitrophenacyl bromide system bonded to a
phosphonium moiety (Table 2) [14].
The 31P NMR spectrum of 2 shows two doublets at 11.52 and
ꢀ30.31 ppm, which are assigned to the PC(H) and PPh2 groups,
respectively. The 1H NMR spectrum shows a doublet at 4.34 ppm
2
2.4.3. Synthesis of [(2)HgX2] {X = Cl (3), Br (4), I (5)}
attributable to the ylidic proton with a coupling constant JP–H of
General procedure for complexes: To
a
solution of HgX2
22.94 Hz. The phosphonium atom of this compound shows upfield
shifts compared to that of parent phosphonium salt (1), suggesting
some increasing of electron density in the P–C bond (Table 2).
The 31P chemical shift values for the complexes appear to be
shifted downfield with respect to the parent ylide, also indicating
that coordination of the ylide has occurred (Table 2). In the 1H
NMR spectra, the signals due to the methinic protons for com-
(0.3 mmol) in methanol (5 ml), a solution of 2 (0.164 g, 0.3 mmol)
in the same solvent (5 ml) was added dropwise at ꢀ5 °C and stirred
for 2 h. The resulting solid was treated with dichloromethane
(35 ml) and filtered through celite. Addition of excess methanol
to the concentrated filtrate caused the precipitation of the products
as pale yellow solids.

S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
1443
Scheme 1.
Scheme 2.
Table 2
Table 1
IR data for compounds 1–6.
Selected 1H and 31P NMR spectral data for compounds 1–5 [d (ppm), J (Hz)].
Compound
m
(CO) cmꢀ1
Reference
Compound d PCH2CO (2JP–H
)
d PCH (2JP–H
)
d PPh2 (2JP–P
)
d PCH (2JP–P
)
Ph2P(CH2)2PPh2C(H)C(O)Ph
Ph2PCH2PPh2C(H)C(O)Ph
1
2
1521
1523
1684
1524
[6]
[6]
This work
This work
1a
6.10 (12.81)
–
ꢀ29.52 (64.57) 20.70 (64.54)
2a
–
–
–
–
4.34 (22.94) ꢀ30.31 (62.47) 11.52 (65.63)
3b
4b,c
5b
5.25 (12.18) 9.07 (br)
5.28 (10.57) 2.45 (br)
21.86 (35.13)
23.15 (43.29)
24.45 (41.01)
5.33 (9.49)
ꢀ1.93 (br)
P-coordinated
[HgBr2(PPh2(CH2)2PPh2C(H)C(O)Ph)]n
[HgI2(PPh2(CH2)2PPh2C(H)C(O)Ph)]n
1511
1504
[15]
[15]
br, broad.
a
Record in CDCl3.
Record in DMSO-d6.
The same data was observed for compound 6 in DMSO solution.
b
c
P, C-coordinated
[HgCl2(PPh2CH2PPh2C(H)C(O)Ph)]
[HgBr2(PPh2CH2PPh2C(H)C(O)Ph)]
[HgCl2(PPh2(CH2)2PPh2C(H)C(O)Ph)]
3
4
5
6
1566
1568
1637
1584
1586
1585
1585
[13]
[13]
[15]
This work
This work
This work
This work
The most interesting aspect of the 13C spectra of the complexes
is the upfield shift of the signals due to the ylidic carbon. Such an
upfield shift observed in [PdCl(
g
3-2-XC3H4)(C6H5)3PCHCOR]
[X = H, CH3; R = CH3, C6H5] was attributed to the change in hybrid-
ization of the ylidic carbon [35]. Similar upfield shifts of 2–3 ppm
with reference to the parent ylide were also observed in the case
of [(C6H5)3PC5H4HgI2]2 [36]. The 13C shifts of the CO group in the
complexes are around 190 ppm (Table 3), relative to 184.05 ppm
noted for the same carbon in the parent ylide, indicating much
lower shielding of the carbon of the CO group in these complexes.
plexes are broad. Similar behavior was observed earlier in the case
of ylide complexes of platinum(II) chloride [34]. The expected low-
er shielding of 31P and 1H nuclei for the PC(H) group upon com-
plexation in the case of C-coordination were observed in their
corresponding spectra.

1444
S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
Table 3
13C NMR data for compounds 1–5.
Compound
1a
2a
3b
4b,c
5b
PCH2P
1JP–C
CH2
1JP–C
CH
21.46(dd)
51.96, 51.96
36.91(d)
60.22
–
–
24.18(dd)
58.19, 51.96
–
22.87(br)
–
–
–
br
–
22.10(br)
–
–
–
br
–
23.33(d)
67.62
–
–
br
–
–
52.78(d)
112.64
181.99(s)
122.99–148.15
1JP–C
CO
191.36(s)
117.27–150.65
189.03(s)
123.48–149.36
186.95(s)
119.07–151.16
189.47(s)
123.06–149.45
Ph
dd, doublet of doublet; d, doublet; br, broad; and s, singlet
a
Record in CDCl3.
Record in DMSO-d6.
The same data was observed for compound 6 in DMSO solution.
b
c
It is clear that the NMR data for complexes 4 and 6 in DMSO
solution should be the same, so an additional NMR data for com-
pound 6 is not reported in Tables 2 and 3. No coupling to Hg was
observed at room temperature in the 1H, 13C and 31P NMR spectra
for all these complexes. Failure to observe satellites in the above
spectra was previously noted in the ylide complexes of Hg(II)
[36] and Ag(I) [37], which had been explained by fast exchange
of the ylide with the metal. Thus, the spectral data indicate the
bidentate coordination of the ligand (2) through both phosphine
group and ylidic carbon atom.
The X-ray analysis in complex 5 reveals the P, C-chelate mode of
coordination of the ligand (2) to Hg(II) atom in this complex. The
Hg(II) center in complex 5 is four-coordinate with sp3 hybridiza-
tion. The Hg atom is surrounded by one P atom of the PPh2 unit,
one ylidic C atom and two I atoms. The angles subtended by the li-
gand at the Hg(II) center in 5 vary from 89.65(17) to 116.17(5)
indicating a distorted tetrahedral environment. The Hg–P bond
length in 5 (2.5199(19) Å) is comparable to analogous distance in
Hg(II)–phosphine complexes [13,38]. In known Hg(II) chelate com-
plexes containing P, O and P, S donors, the Hg–P distances vary
from 2.404(1) Å, as in trans-[Hg{Ph2PNP(O)Ph2}2] [39], to
2.503(5) Å as in [HgI2{Ph2PCH2P(S)Ph2}] [40]. The Hg–C bond dis-
tance in 5 (2.446(8) Å) is longer than average of those found in a
number of dinuclear or trinuclear Hg–phosphoylide compounds,
2.2 Å [20,32,36,41].
The X-ray analysis in complex 6 reveals the P, C-coordination
of the ligand to the mercury ion. However, in this compound due
to coordination of DMSO molecule to the metal ion the Hg–C
bond length, 2.872 Å, is considerably weakened in comparison
with compound 5 (2.446(8) Å) and other complexes (an average
of 2.4 Å) [13]. As can be seen in Fig. 2, the ylidic carbon and oxy-
gen atom of the coordinated DMSO molecule are located in the
3.3. X-ray crystallography
Suitable crystals were obtained from dimethylsulfoxide solu-
tion by the slow evaporation of the solvent over several days. Table
4 provides the crystallographic results and refinement information
for complexes 5 and 6. The molecular structures are shown in Figs.
1 and 2. Pertinent bond distances and angles for 5 and 6 are given
in Table 5. Fractional atomic coordinates and equivalent isotropic
displacement coefficients (Ueq) for the non-hydrogen atoms of
the complexes are shown in Supplementary material.
Table 4
Crystal data and refinement details for 5 and 6.
Compound
5
6
Empirical formula
Formula weight
Temperature (K)
Wavelength (Å)
Crystal system
Space group
a (Å)
C33H27HgI2NO3P2
1001.89
150(2)
0.71073
Monoclinic
C35H33Br2HgNO4P2S
986.03
150(2)
0.71073
Monoclinic
P21/c
9.5319(2)
P21/c
13.3138(3)
b (Å)
15.6912(3)
17.6760(4)
c (Å)
16.0974(3)
21.5859(7)
a
(°)
90
90
b (°)
103.479(2)
99.039(3)
c
(°)
90
90
Z
4
4
Absorption coefficient (mmꢀ1
h range for data collection (°)
Index ranges
)
6.726
3.00–25.05
ꢀ15 6 h 6 15
ꢀ13 6 k 6 18
ꢀ13 6 l 6 19
15 032
6.696
2.99–25.00
ꢀ10 6 h 6 11
ꢀ13 6 k 6 20
ꢀ25 6 l 6 14
Reflections collected
16 511
Independent reflections (Rint
Absorption correction
)
5780 (0.0271)
Semi-empirical from equivalents
0.4319 and 0.3943
Full-matrix least-squares on F2
1.047
6306 (0.0539)
Semi-empirical from equivalents
0.5263 and 0.2964
Full-matrix least-squares on F2
0.923
Maximum and minimum transmission
Refinement method
Goodness-of-fit on F2
Final R indices [I > 2
R indices (all data)
r
(I)]
R1 = 0.0427, wR2 = 0.1096
R1 = 0.0565, wR2 = 0.1141
1.491 and ꢀ2.910
R1 = 0.0456, wR2 = 0.0752
R1 = 0.0889, wR2 = 0.0821
1.879 and ꢀ1.400
Largest difference in peak and hole (e Åꢀ3
)

S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
1445
Fig. 1. ORTEP view of X-ray crystal structure of 5. Hydrogen atoms are omitted for reasons of clarity.
Table 5
Selected bond lengths (Å) and bond angles (°) for 5 and 6.
Complex 5
Hg(1)–C(26)
2.446(8)
Hg(1)–P(1)
Hg(1)–I(1)
Hg(1)–I(2)
P(2)–C(26)
2.5199(19)
2.7070(7)
2.6946(9)
1.764(7)
O(1)–C(27)
1.231(9)
C(26)–Hg(1)–P(1)
C(26)–Hg(1)–I(1)
C(26)–Hg(1)–I(2)
P(1)–Hg(1)–I(1)
P(1)–Hg(1)–I(2)
I(1)–Hg(1)–I(2)
C(1)–P(1)–Hg(1)
C(2)–P(1)–Hg(1)
C(26)–P(2)–C(1)
C(27)–C(26)–P(2)
89.65(17)
112.69(17)
108.68(18)
114.17(5)
116.17(5)
113.12(3)
101.1(2)
116.8(3)
111.7(4)
112.1(5)
Complex 6
Hg(1)–P(1)
2.4385(19)
2.5664(9)
2.5609(8)
1.737(7)
1.241(8)
1.531(6)
125.80(5)
128.71(5)
104.17(3)
107.1(2)
115.5(2)
112.0(3)
115.2(5)
Hg(1)–Br(1)
Hg(1)–Br(2)
P(2)–C(26)
O(1)–C(27)
O(4)–S(1)
P(1)–Hg(1)–Br(1)
P(1)–Hg(1)–Br(2)
Fig. 2. ORTEP view of X-ray crystal structure of 6. Hydrogen atoms are omitted for
reasons of clarity.
Br(1)–Hg(1)–Br(2)
C(1)–P(1)–Hg(1)
C(2)–P(1)–Hg(1)
C(26)–P(2)–C(1)
C(27)–C(26)–P(2)
axial positions of the resulting trigonal bipyramidal complex.
Thus the Hg–O bond length, 3.060 Å, similar to Hg–C bond
length is considerably elongated and is longer than expected va-
lue for coordinated DMSO molecule [18,42]. In the equatorial
positions the Hg(II) atom is also surrounded by one phosphorous
atom of the PPh2 unit and two terminal Br atoms. Thus this
(2.519(19) Å), indicating relatively strong Hg–P bond in this
complex. It is worth noting that in 6, the S–O bond distance of
1.531(36) Å, is about 0.022 Å longer than the experimental refer-
ence value of 1.492(1) Å for free DMSO ligand [44].
compound can be considered as
a pseudo five-coordinate
complex. The C(26)–Hg–O(4) bond angle is 156.14 and the
angles subtended by the ligand at the Hg(II) center in the equa-
torial positions are 104.17(3), 125.80(5) and 128.71(5), indicating
a distorted trigonal bipyramidal environment. The Hg–P bond
distance in 6, 2.438(19) Å, is less than those found in
complexes of [HgBr2(PPh3)2] (2.540(16) and 2.535(15) Å) [43],
The two terminal Hg–X distances in
5 (2.694(9) and
2.707(7) Å) and in 6 (2.560(8) and 2.566(4) Å) are comparable
to analogous distances in [HgI2(PPh3)2] (2.733(1) and
2.763(1) Å) [45] and [HgBr2(PPh3)2] (2.626(8) and 2.633(6) Å)
[43].
[HgI2(PPh2(CH2)2PPh2C(H)C(O)Ph)]n (2.472(2) Å) [15] and
5

1446
S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
Fig. 3. Calculated molecular structures of (a) 2, (b) 3, (c) 4, (d) 5, (e) 6, (f) 7, and (g) 8.

S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
1447
Table 6
assume that two new compounds, [(2)HgCl2DMSO] (7) and
[(2)HgI2DMSO] (8), can be produced with the reaction of com-
pounds 3 and 5 with DMSO molecule, respectively.
The optimized structures for compounds 2–8 are shown in
Fig. 3. The optimized structure parameters for latter compounds
calculated by DFT method listed in Tables 6–8 are in accordance
with atom numbering scheme given in ORTEP views of compounds
5 and 6 (Figs. 1 and 2). Results of optimization energy for com-
pound 5 (energy vs. optimization steps) were presented in Supple-
mentary material (Fig. 1S).
A comparison between the selected calculated bond lengths (Å)
and bond angles (°) for complexes 3–8 with corresponding exper-
imental values for complexes 5 and 6 are presented in Tables 6 and
7. As it can be seen, the calculated structures using CEP-121G basis
set for both complexes 5 and 6 in the gas-phase have better agree-
ment with the structures determined by X-ray crystallography
than those derived from LanL2DZ calculations. Thus for other com-
plexes 3, 4, 7 and 8, we reported only the results of CEP-121G cal-
culations. In order to show the changes in the structure of ylide (2)
upon coordination to metal ion, a comparison between the selected
calculated bond lengths and bond angles for it and corresponding
complexes 3–8 is also given in Table 8. As can be seen (Table 8),
the stabilized resonance structure for the parent ylide (2) is de-
stroyed by the complex formation, thus, the C(26)–C(27) bond
lengths 1.466 Å (3), 1.467 Å (4), 1.461 Å (5), 1.460 Å (6), 1.476 Å
(7) and 1.420 Å (8) are longer than the corresponding distance
found in the parent ylide (2) [1.412 Å]. On the other hand, the
C(26)–P(2) bond length in the free ylide is 1.799 Å and is elongated
to 1.852, 1.854, 1.852, 1.843, 1.859, 1.807 Å and in compounds 3, 4,
A comparison between the selected calculated bond lengths (Å) and bond angles (°)
for compounds 3, 4 and 5 and corresponding experimental values for complex 5.
3
4
5
CEP-121G CEP-121G CEP-121G LanL2DZ X-ray
Bond lengths
Hg(1)–C(26)
Hg(1)–P(1)
Hg(1)–X(1)a
Hg(1)–X(2)a
P(2)–C(26)
O(1)–C(27)
2.489
2.884
2.537
2.501
1.852
1.289
2.499
2.926
2.617
2.663
1.854
1.288
2.563
2.947
2.817
2.779
1.852
1.230
2.730
3.035
2.839
2.879
1.825
1.287
2.446
2.520
2.707
2.695
1.764
1.231
Bond angles
C(26)–Hg(1)–P(1)
85.13
84.08
118.65
106.90
102.91
110.85
125.18
82.26
114.60
109.75
103.72
111.67
125.85
78.80
113.98
107.95
104.06
110.78
129.43
89.65
112.69
108.68
114.17
116.17
113.12
C(26)–Hg(1)–X(1)a 112.09
C(26)–Hg(1)–X(2)a 108.14
P(1)–Hg(1)–X(1)a
P(1)–Hg(1)–X(2)a
103.33
107.21
X(1)a–Hg(1)–X(2)a 130.78
a
X in the compounds 3, 4 and 5 is Cl, Br and I, respectively.
Table 7
A comparison between the selected calculated bond lengths (Å) and bond angles (°)
for compounds 6, 7 and 8 and corresponding experimental values for complex 6.
6
7
8
CEP-121G LanL2DZ X-ray
CEP-121G CEP-121G
Bond lengths
Hg(1)–P(1)
Hg(1)–C(26)
Hg(1)–O(4)
Hg(1)–X(1)a
Hg(1)–X(2)a
P(2)–C(26)
O(1)–C(27)
O(4)–S(1)
2.871
2.576
2.541
2.664
2.775
1.843
1.291
1.739
3.026
2.750
2.470
2.748
2.791
1.817
1.291
1.720
2.438
2.872
3.060
2.566
2.561
1.737
1.241
1.531
3.095
2.392
2.416
2.553
2.800
1.860
1.285
1.737
2.863
3.488
2.546
2.760
2.823
1.807
1.309
1.730
Table 9
Calculated electronic energies for four-coordinate complexes, DMSO and pseudo five-
coordinate complexes involved in Eq. (1).
Bond angles
P(1)–Hg(1)–C(26)
P(1)–Hg(1)–X(1)a
P(1)–Hg(1)–X(2)a
P(1)–Hg(1)–O(4)
83.08
106.74
132.21
70.00
76.68
100.54
138.88
80.75
147.25
88.79
114.34
92.79
92.93
84.04
125.80
128.71
77.30
156.14
90.79
108.83
94.22
89.42
81.508
99.88
144.31
77.42
135.33
86.20
126.31
96.06
71.41
109.66
117.27
70.78
139.14
84.53
105.92
100.484
99.42
Compound [(2)HgX2]
DMSO
(hartree)
[(2)HgX2DMSO]
(hartree)
DE
(hartree)
(kcal molꢀ1
)
X = Cl
X = Br
X = I
ꢀ456.707
ꢀ453.635
ꢀ449.769
ꢀ40.891
ꢀ40.8901
ꢀ40.891
ꢀ497.624
ꢀ494.549
ꢀ490.672
16.47
14.54
7.42
C(26)–Hg(1)–O(4) 146.02
C(26)–Hg(1)–X(2)a
91.66
C(26)–Hg(1)–X(1)a 112.45
X(1)a–Hg(1)–O(4)
X(2)a–Hg(1)–O(4)
95.34
91.49
88.54
114.26
X(1)a–Hg(1)–X(2)a 118.91
120.41
104.17
132.72
Table 10
a
X in the compounds 6, 7 and 8 is Br, Cl and I, respectively.
HOMO, LUMO and gap energy of the optimized structure of compound 2–5 at the
B3LYP/CEP-121G level of theory.
Species
Value
3.4. Theoretical studies
2
3
4
5
HOMO (eV)
LUMO (eV)
H–L (eV)
ꢀ5.667
ꢀ2.941
2.726
ꢀ6.553
ꢀ3.251
3.302
ꢀ6.332
ꢀ3.271
3.061
ꢀ6.010
ꢀ3.259
2.751
As it discussed in previous section the compound 6 is product of
the reaction of DMSO molecule with compound 4. We were inter-
ested to study the latter reaction for compounds 3 and 5. We can
Table 8
A comparison between the selected calculated bond lengths (Å) and bond angles (°) for ligand 2 and corresponding complexes (3–8).
2
3
4
5
6
7
8
Bond lengths
C(26)–C(27)
P(2)–C(26)
P(2)–C(1)
P(1)–C(1)
O(1)–C(27)
1.412
1.799
1.902
1.941
1.311
1.466
1.852
1.893
1.927
1.289
1.467
1.854
1.893
1.926
1.288
1.461
1.852
1.890
1.927
1.291
1.460
1.843
1.897
1.916
1.291
1.476
1.420
1.807
1.901
1.919
1.309
1.859
1.892
1.929
1.285
Bond angles
C(1)–P(2)–C(26)
P(2)–C(26)–C(27)
P(1)–C(1)–P(2)
115.22
116.75
113.70
111.15
110.32
112.54
111.16
110.62
112.70
111.83
110.37
112.45
110.36
110.91
110.55
111.10
111.13
111.38
112.17
113.52
115.31

1448
S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
Fig. 4. Illustration of calculated (a) HOMO and (b) LUMO for compound 5.
Fig. 5. Electronic density of states (EDOS) of (a) 4, (b) 5, and (c) 2. Blue lines represent virtual orbitals, green lines represent occupied orbitals and a red line represents DOS
spectra. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

S.J. Sabounchei et al. / Journal of Organometallic Chemistry 695 (2010) 1441–1450
1449
5, 6, 7 and 8, respectively. Obviously, the significant changes in the
bond lengths and bond angles of the parent ylide due to complex-
ation must be found around the coordinated part of the ligand {i.e.
C(26)–P(2)–C(1)–P(1) moiety}. The changes in bond lengths and
bond angles calculated here are very similar to those observed
for the complexes of similar ylides [13,18].
molecule with complex (4) and formation of a pseudo five-coordi-
nated complex (6) is an exothermic reaction and is potentially pos-
sible for present complexes.
Acknowledgements
As we explained in previous sections the complex 6 is the prod-
uct of the crystallization of the compound 4 in DMSO solution. The
results of present calculations show that the product of the follow-
ing proposed reaction (Eq. (1)) is about 16.47, 14.54 and 7.42 kcal/
mol more stable than reactants for compounds 3, 4 and 5, respec-
tively (see Table 9).
The authors thank Ms. M. Borowski (Department of Chemistry,
Technische Universität Berlin) for her invaluable support in X-ray
experiments. We are grateful to the Bu-Ali Sina University for a
grant, Mr. Zebarjadian and Darvishi for recording the NMR spectra.
Appendix A. Supplementary material
rt
½ð2ÞHgX2ꢁ þ DMSO !½ð2ÞHgX2DMSOꢁ:
ð1Þ
CCDC 703481 and 717739 contain the supplementary crystallo-
graphic data for complexes 5 and 6. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre
via http://www.ccdc.cam.ac.uk/data_request/cif.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.jorganchem.2010.02.029.
Thus, it is clear that for all compounds synthesized here, the
gas-phase reaction shown in Eq. (1) is an exothermic reaction.
Therefore the coordination of the DMSO molecule to the central
Hg(II) metal ion and weakening of the Hg–C bond length is ener-
getically favored for all compounds 3, 4 and 5. However, we could
not isolate the products of latter reaction in the case of compounds
3 and 5.
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The energies of the HOMO and LUMO for ligand (2) and com-
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gand. As can be seen in Table 10, the calculated energy gap be-
tween the latter orbitals for complexes 3, 4 and 5 is 3.302, 3.061,
2.751 (eV), respectively. Thus, as expected the complex including
iodine as a ligand is softest compound and that including chlorine
ligand is hardest one. This is completely consistent with this fact
that a hard group makes molecule hard and a soft groups makes
it soft. However, it is interesting that the energy of LUMO, the tar-
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compound 4. Thus it can be probably a reason for this fact that we
have observed the DMSO reaction only for latter compound. But as
we mentioned above it seems that the reaction of DMSO molecule
with all compounds 3, 4 and 5 is potentially possible. Three-
dimensional pictures of the HOMO and LUMO for 5 are presented
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of Eg, indicating that the charge transfer was occurred. Compared
DOS of complexes 4 and 5 with ligand show that significantly
change in Fermi level and position of the sharp peaks were
occurred.
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